1. Field of the Invention
The invention relates to optical sample detectors used in various fields of life and analytical sciences, in particular medical and biomedical assays. In particular, the invention relates to sample analysers capable of fluorescence measurements.
2. Prior Art
Analysers of the present kind are commonly adapted to detect light successively from each one of a plurality of sample sites contained in the microplate. Therefore, they are frequently called as microplate “readers”. One example or such a system is the EnVision-reader and its variants available from PerkinElmer.
The present commercial microplate readers typically include a broad-band excitation light source. Different kinds of optical arrangements for manipulating and guiding light from the light source to the sample sites are disclosed in US 2003/0081207, U.S. Pat. No. 6,232,608, WO 00/63680, US 2002/0109841, U.S. Pat. No. 6,313,471, WO 2005/057187, U.S. Pat. No. 6,097,025 and WO 2003/027724. For example, U.S. Pat. No. 6,097,025 discloses a measurement apparatus having a plurality of light sources and an optical path switching mechanism comprising a slidable shuttle.
U.S. Pat. No. 5,475,221 discloses an apparatus having an array of LEDs and an Acousto-Optic Tunable Filter (AOTF) controlled by multiplexing means to obtain a broadband spectrometer.
In addition BioTek Instruments Inc. has published a Synergy™ 4 Multi-Detection Microplate Reader. The system is provided with a Xenon flash as its light source and it combines both filter-based and quadruple monochromator-based fluorescence detection technology.
Each particular type of light source has its own advantages and disadvantages and allows for certain types of measurements, i.e. measurement modes, to be carried out. Moreover, a single light source can be used in several measurement modes, depending on how the light is guided to the sample and how light is collected from the sample. Apparatuses according to the prior art have the disadvantages that they are limited either to one light source or that the changing of light source used and/or the measurement mode is either difficult or accomplished in a complex way. Thus, the prior optical solutions are as such not well suitable for modern multi-purpose apparatuses intended to allow for carrying out diverse optical measurements in different optical configurations.